Aromatase and oestrogens in human male germ cells.

The mammalian testis serves two main functions: production of spermatozoa and synthesis of steroids, among them oestrogens are the end products obtained from the irreversible transformation of androgens by aromatase (P450arom). Up today P450arom has been demonstrated in male germ cells of all mammals so far studied (mice, rat, bank vole, bear, monkey). In man Leydig cells and immature germ cells as well as ejaculated spermatozoa express a biologically active aromatase. Moreover germ cells and spermatozoa contain oestrogen receptors (ER-alpha and ER-beta) and it is of note that a truncated form of ER-alpha is present in spermatozoa. These observations clearly suggest that oestrogens are likely concerned in various stages of male germ cell development.